View Construct

Question

I Read somewhere
In Oracle SQL no insert, update, or delete modifications on views are allowed
that use one of the following constructs in the view definition:
• Joins
• Aggregate function such as sum, min, max etc.
• set-valued subqueries (in, any, all) or test for existence (exists)
• group by clause or distinct clause
But When i create view by joining 2 tables or by subquery it let you manipulate insert,update or delete.
So i want to ask what is written above for view construct by joining or by subquery is right or not or there is version difference though i am using Oracle9i Enterprise Edition Release 9.2.0.1.0.
My next question is how can we create view read only?
Thanx
Regards
Khurram Siddiqui

Answer 1

From the Oracle Manual:
If you want a join view to be updatable, all of the following conditions must be true:
- The DML statement must affect only one table underlying the join.
- For an INSERT statement, the view must not be created WITH CHECK OPTION, and all columns into which values are inserted must come from a key-preserved table. A key-preserved table in one for which every primary key or unique key value in the base table is also unique in the join view.
- For an UPDATE statement, all columns updated must be extracted from a key-preserved table. If the view was created WITH CHECK OPTION, join columns and columns taken from tables that are referenced more than once in the view must be shielded from UPDATE.
- For a DELETE statement, if the join results in more than one key-preserved table, then Oracle deletes from the first table named in the FROM clause, whether or not the view was created WITH CHECK OPTION
To create a non-updateable view, you can use the "read only" clause. E.g. :
CREATE VIEW test_v (test_col)
AS SELECT v1
FROM test_t
WITH READ ONLY;
Hope this helps.